While total U.S.-listed ETF assets have been reaching record levels this year—most recently just shy of $1.349 trillion on Dec. 18—closures have been accelerating while fund launches have been slowing.

Industry sources say the industry is starting to mature and, moreover, the risk-on/risk-off flavor of markets since the 2008 crash has made fund sponsors more cautious in general about launching new ideas or defending ones that aren’t catching on very quickly.

Moreover, pruning product offerings can free up resources for fund sponsors to pursue newer, more prospective fund ideas more thoroughly and aggressively.